1. Field of the Invention
This invention relates to a skate wheel and more particularly to a high performance in-line skate wheel having a shaped foam core which cooperates with the surrounding polyurethane load bearing side walls to dictate degrees of compression of the flexure of such walls in response to loading thereof from different directions.
2. Description of the Prior Art
Roller skates and roller skate wheels have been known in the art. Early roller skates incorporated four wheels disposed in a box-like pattern. Inflatable rubber roller skate wheels encased in a thin rubber wall tire, such as that disclosed in U.S. Pat. No. 988,533 to Zverina, was proposed as a simple, durable wheel. Such wheels failed to gain general acceptance.
In the past, many skate wheels were constructed of rubber. The availability of polyurethane in skate wheel construction has enhanced the enjoyment and popularity of outdoor skating. The typical roller skates having four wheels in a box-like pattern do not allow for the freedom of movement experienced by ice skaters utilizing single blade skates. It was thus proposed to mount the roller skate wheels in a line along the skate frame to achieve mobility which closely mimicked the movement of an ice skate. Since that time, "in-line roller skates" have become one of the most popular recreational and physical fitness activities in the United States, and elsewhere. In-line skating has also developed into a highly sophisticated and technologically advancing commercial market.
The recreational skater often travels a variety of terrains ranging from concrete and wood to more bumpy and uneven surfaces such as asphalt which may exhibit bumps, pits and even wide cracks with vegetation growing therein. The main concern experienced by the recreational skater is to obtain a comfortable ride while skating socially, participating in physical fitness or even just a way to reach a destination. This skater requires a resilient wheel which is light weight and shock resistant. More experienced skaters, such as competitive skaters, employ in-line skates for sporting purposes such as hockey or road racing. Dancers typically prefer relatively hard tire bodies since some slippage is an acceptable compromise for the performance required. On the other hand, the high speed skating acrobatic maneuvers normally associated with hockey players could be best performed with a tire having relatively little resistance to deformation when in the upright position normally associated with a relatively straight skating path but which, when leaned over on the side, exhibit a greater degree of deformation to generate a larger footprint for more effective gripping to avoid slippage.
Polyurethane in-line skate wheels proposed in the past have typically been constructed by injection molding to form a hub surrounded by a tire body of solid urethane. It is desirable that such wheels provide a durable and relatively smooth ride over many types of terrains. Such tire bodies are necessarily restricted in that the performance characteristics cannot be easily and inexpensively adjusted during the manufacturing process to accommodate the many different support surfaces and loads encountered by a skate employed in a demanding sport such as, for instance, hockey.
It has been proposed to construct an in-line skate wheel with a nylon hub having an annular gridwork defining axially through passages for receiving cross segments of urethane embodied in a tire body. A wheel of this type is shown in U.S. Pat. No. 5,028,058 to Olson. Wheels of this type, while satisfactory for their intended purposes, do not typically exhibit the durability and performance characteristics important to aggressive athletic roller skating activities, such as roller hockey and the like.
Other efforts to improve polyurethane wheels have led to the proposal that polyurethane be injected into a mold around a hard polyurethane hub having an annular grid work for interlocking of the resultant tire body with the hub to create an interlocked solid tire body. A device of this type is shown in U.S. Pat. No. 5,312,844 to Gonsior. Wheels of this type, while being acceptable for recreational skating activity, are relatively expensive to manufacture and do not provide a tire which will deform to different degrees when loaded from different directions to provide correspondingly different resistances to rolling and different gripping characteristics.
Other efforts in polyurethane wheel design has led to the proposal of a hard polyurethane hub formed with a radially projecting annular ring configured with transverse through bores for flow of a molten thermoplastic polyurethane tire material therethrough for mechanical interlocking thereof. A wheel of this type is shown in U.S. Pat. No. 5,567,019 to Raza. Wheels of this type, while satisfactory for recreational skating, are relatively expensive to manufacture and exhibit a relatively hard peripheral surface which provides for only limited cushioning and flexibility to accommodate irregular terrain and flexure to exhibit a relatively large foot print upon tight high speed turns for positive gripping of the underlying terrain.
Still other attempts have been made to provide a tire which is capable of optimal performance over a variety of skating surfaces, skating conditions and skating maneuvers as recited in U.S. Pat. No. 5,573,309 to Bekessy. This patent discloses a wheel with a hub having a tapered tire deflection controlling rim encapsulated by a tire formed of a solid resilient material such as urethane. The tire defection controlling rim extends radially in an annular fashion from lateral tire receiving shoulders and cooperates with the surrounding tire body to influence tire deflection. During straight line skating, when the wheels roll in a substantially vertical orientation, the effective vertical tire thickness is minimized and tire deflection is limited to keep frictional resistance low. However when the skater leans the tire over during turning maneuvers the rigid deflection controlling features allows for only limited tire deformation capability thus limiting the gripping characteristic of the tire.
Other designs have led to cushioned wheels which incorporate shock absorbing annular elements located between the outer walls of a hub and the inner surfaces of two half shells. The half shells also create a cavity which slidably receives a diaphragm which extends radially outwardly from the hug. A covering layer of thermosetting polyurethane forms a tire which does not contact the hub but instead surrounds the outer surfaces of the two half shells. A wheel of this type is show in U.S. Pat. No. 5,560,685 to De Bortoli. In operation these wheels require relatively complex component interaction are relatively expensive to manufacture.
In recognition of the desirability of an in-line skate wheel which combines the resiliency and performance of a polyurethane wheel with the enhanced grip, durability and shock absorption properties associated with hollow body wheel construction and which can be casted from thermoplastic polyurethane, applicants propose a solution in U.S. Pat. No. 5,630,891, assigned to the assignee of the instant application. That patent discloses an in-line skate wheel with an adjustable toric bladder encapsulated in a thermoplastic polyurethane wheel body. Pressure in the bladder is adjustable through the use of a valve system. Such a wheel allows the skater to adjust wheel performance to match his or her needs for the particular skating maneuver to be undertaken. Since the skater has multiple performance options available without purchasing multiple wheels and without having to manually change the skate wheels, such a wheel is versatile, cost effective and convenient. While having important commercial applications, it is recognized that such an adjustable pneumatic in-line skate wheel requires the skater to manipulate the wheel each time skate conditions change and the wheel itself is relatively costly to manufacture.
Another form of an in-line skate wheel with similar urethane and pneumatic benefits can be found U.S. Pat. No. 5,641,365, also assigned to the assignee of the instant application. In that application, a pre-pressurized pneumatic in-line skate wheel of integral construction was shown consisting of an hub mounting an annular toric bladder via a plurality of radially projecting spoke-like bladder rods encapsulated in a thermoplastic polyurethane tire body. It is a characteristic of such pressurized bladders that when pressurized they tend to take a round cross sectional shape so that the resilient wheel, while light weight and presenting excellent shock absorptive characteristics, is limited in ability to adjust the shape of the cross sectional interior and consequent shape of the tire wall for preferential flexing of different portions thereof as loads are applied thereto from different directions.
In other areas of the art, such as in the construction of variable pressure athletic shoes, it has been known to provide elastomeric bladders configured with multiple discrete chamber or open cell elastomeric foam having inlet and outlet valves. Devices of this type are shown in U.S. Pat. Nos. 4,183,156 and 4,287,250 to Rudy and U.S. Pat. No. 5,144,708 to Pekar. However, such bladders have not been generally adapted to or employed in skate wheel construction.
Thus, there exists a need for a skate wheel which can be inexpensively molded from thermoset polyurethane to provide a thick cushion like load bearing wall having a polygonal in cross section annular cavity cooperating to provide such wall with different degrees of flexure depending on whether loaded along the central plane of the wheel or at an acute angle to such central plane.
This need could be best satisfied by an in-line skate wheel which combines the benefits of a large deflection when the wheel is leaned over on a high speed turn to thus grip the support surface but which will compress only slightly when oriented in an upright position normally associated with straight line skating to thus minimize resistance to rolling.